U.S. patent number 4,834,722 [Application Number 07/142,311] was granted by the patent office on 1989-05-30 for injection assembly for blocking peripheral nerves, for instance for plexus anaesthesia.
Invention is credited to Michael Zenz.
United States Patent |
4,834,722 |
Zenz |
May 30, 1989 |
Injection assembly for blocking peripheral nerves, for instance for
plexus anaesthesia
Abstract
An injection device is described for the blocking of peripheral
nerves, e.g., for plexus anaesthesia. This injection device has an
injection needle of metal which is provided at one end with a
needle tip and at the opposite end with a base part for the
connection of a syringe. In order in this injection device to
largely eliminate the danger of damage to nerve fibers or injury to
blood vessels by the injection needle and to permit an additional
aid by the positive location of the plexus, the needle tip is
formed by a ground surface inclined at an angle of 40.degree. to
60.degree., preferably of 45.degree. to 50.degree., to the cannula
axis.
Inventors: |
Zenz; Michael (D-3000 Hannover
58, DE) |
Family
ID: |
6725401 |
Appl.
No.: |
07/142,311 |
Filed: |
December 28, 1987 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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355254 |
Mar 5, 1982 |
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Foreign Application Priority Data
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Mar 7, 1981 [DE] |
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8106577[U] |
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Current U.S.
Class: |
604/272; 604/533;
604/239 |
Current CPC
Class: |
A61M
5/158 (20130101); A61M 5/3286 (20130101) |
Current International
Class: |
A61M
5/14 (20060101); A61M 5/158 (20060101); A61M
5/32 (20060101); A01M 005/00 () |
Field of
Search: |
;604/239,240,241,272,273,274,904,280,283 ;128/339 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
M J. Cousins and P. O. Bridenbaugh, "Neural Blockade", 1980, pp.
296-310..
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Primary Examiner: Pellegrino; Stephen C.
Parent Case Text
This application is a continuation-in-part of application Ser. No.
355,254, filed Mar. 5, 1982, now abandoned.
Claims
I claim:
1. A plexus anaesthesia needle for the injection of a local
anaesthetic for blocking peripheral nerves, said needle consisting
of metal and having a first end with means for connection of a
syringe and a free second end with a needle tip, a continuous
passage extending along an axis from the first end to the needle
tip, the length of said needle between said first end and said
needle tip being approximately 25 to 50 mm; said needle being of a
size gauge 24 to 26 and having an outer diameter of approximately
0.55 mm; said needle tip being formed by a circumferential surface
of said needle substantially coaxial with said axis and a ground
surface inclined at an angle to said axis;
wherein the improvement comprises: the angle of inclination of said
ground surface to said axis ranging from 40.degree. to 60.degree.
such that, at least in the area of the outermost end of the needle
tip, a nerve will tend to roll away from the inclined ground
surface as the needle tip approaches, and the needle tip is moved
past the nerve without nerve lesions.
2. A plexus anaesthesia needle according to claim 1, in which said
angle of inclination ranges between 45.degree. and 50.degree..
3. A plexus anaesthesia needle according to claim 1, in which the
outermost end of the needle tip is slightly rounded or dulled.
4. The combination of:
(a) a plexus anaesthesia needle for the injection of a local
anaesthetic for blocking peripheral nerves, comprising: a
substantially cylindrical injection needle of metal having a first
end on which a needle tip is formed, a second end on which a
connection portion is formed, and a needle bore extending
longitudinally approximately concentrically through said needle
substantially to both needle ends, the length of said needle
between said needle ends being approximately between 25 and 50 mm;
said needle being of a size gauge 24 to 26 and having an outer
diameter of approximately 0.55 mm; said needle tip being defined by
a circumferential surface of said needle substantially concentric
with a longitudinal axis of the needle bore and a ground surface
inclined at an angle to said axis;
(b) a connection component of plastic for receiving the local
anaesthetic and for introduction of the anaesthetic into the needle
bore, said connection component being glued or cemented to the
second end of the injection needle and having a central tapered
socket which communicates with the bore and flares funnel-wise
toward the receiving side; and
(c) a prolongation structure for connecting a syringe containing
the local anaesthetic to said connection component, the
prolongation structure containing an elongated, flexible conduit in
the form of a flexible plastic tube to whose one end first coupling
means are disposed for releasable coupling with said connection
component and on whose other end second coupling means are disposed
for releasable connection of a syringe, said flexible plastic tube
helping to hold the injection needle immobile upon a movement of
the second coupling means;
wherein the improvement comprises: the angle of inclination of the
ground surface to the needle axis ranging between 40.degree. to
60.degree., thereby reducing the danger of nerve lesions and
facilitating the location of the plexus.
5. The combination according to claim 4, wherein the tapered socket
of the connection component is limited outwardly by a fastening
flange, the first coupling means having an axially projecting
tubular tapered chuck communicating with the flexible tube, said
chuck being adapted to be inserted into the tapered socket axially,
and a screw cap concentrically surrounding the tubular tapered
chuck at a distance therefrom, which is adapted to be screwed onto
the fastening flange of the connection component, thereby drawing
the tubular tapered chuck into the tapered socket and producing a
leak-proof coupling between the chuck and the tapered socket.
6. The combination according to claim 5, wherein said second
coupling means of the prolongation structure have a tapered socket
limited by a fastening flange, and having the same shape and
construction as said connection component and flaring funnel-wise
toward the receiving end.
7. The combination according to claim 4, wherein said flexible
plastic tube has a length ranging from about 20 to 35 cm.
8. The combination according to claim 4, in which said angle of
inclination is 45.degree. to 50.degree..
9. The combination according to claim 4, in which the outermost end
of the needle tip is slightly rounded or dulled.
10. An injection device for the blocking of peripheral nerves,
comprising:
(a) a substantially rigid injection needle of metal which has at a
distal end a relatively short needle tip and on the opposite end a
socket and is provided with an axial bore connecting the two needle
ends, the length of said needle between said needle ends being
approximately between 25 and 50 mm; said needle being of size gauge
24 to 26 and having an outer diameter of approximately 0.55 mm;
said needle tip being defined by a substantially cylindrical
circumferential surface concentric with a longitudinal axis of said
needle and a ground surface intersecting the circumferential
surface at an angle; and
(b) a flexible plastic tube connected in a liquid-tight manner to
the connection end of the injection needle and having a length
ranging from 20 to 35 cm, to which the end remote from the
injection needle is provided with coupling means for the connection
of an injection syringe and forms an outwardly leak-proof conduit
connection from an injection syringe to the injection needle, means
being provided for sealing off the coupling points between the
injection needle and the flexible plastic tube as well as at the
coupling means of the plastic tube;
wherein the improvement comprises: the angle of inclination of the
ground surface to said needle axis ranging from 40.degree. to
60.degree..
11. An injection device according to claim 10, wherein the length
of said needle is 35 mm.
12. An injection device according to claim 10, in which said angle
of inclination is 45.degree. to 50.degree..
13. An injection device according to claim 10, in which the
outermost end of the needle tip is slightly rounded or dulled.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the field of the blocking of peripheral
nerves, for example the field of plexus anaesthesia, and especially
to an injection device having an injection needle of metal which
has at one end a base for the attachment of a syringe, and at the
opposite end an especially shaped needle tip.
2. State of the Art
Plexus blocks are used in anaesthesia in operations on the arm and
hand, for example, especially when urgent operations must be
performed on patients who are not fasting. In spite of undisputed
advantages, plexus blocks with so-called immobile needles have been
successfully practiced only in exceptional cases and by very
experienced anaesthetists, since the tip of the injection needle or
cannula has, under certain circumstances, caused severe injuries to
the nerve fibers and blood vessels as well as degenerative changes
in and discontinuities of the fibers.
Conventional injection needles usually have a tip which is defined
by a cylindrical circumferential surface and a surface made by
grinding at an angle of less than 20.degree. to the cannula axis.
The inventor has found through tests that the main reason for
lesions to nerve fibers and blood vessels in plexus anaesthesia
using the known injection needles is that the needles have very
sharp tips. Such sharp needle tips "skewer" even thin nerve fibers
and blood vessels instead of turning them aside.
SUMMARY OF THE INVENTION
It is an object of the invention to create an improved injection
device for the blocking of peripheral nerves.
It is another object of the invention to construct the needle tip
such that the danger of nerve lesion is reduced or even largely
eliminated, and an additional aid is created by the positive
location of the plexus.
An additional object of the invention consists in providing the
injection cannula with a short and flexible prolongation through a
LuerLok coupling, so that the cannula can be held in position
unaffected by the palpation.
An injection device is offered for the blocking of peripheral
nerves, e.g., for plexus anaesthesia. This injection device has a
needle of metal which is provided at one end with a sharp tip and
at the opposite end with a base for the attachment of a syringe.
The needle tip is defined by an approximately cylindrical
circumferential surface and a surface made by grinding which is
inclined at a relatively blunt angle of approximately 40.degree. to
60.degree. degrees from the needle or cannula axis. The relatively
blunt bevel on the needle tip offers a greater resistance to the
piercing of the skin than conventional needles. A nerve will roll
aside from the approaching injection needle and its beveled tip, so
that the needle tip moves past the nerves without damaging or
injuring them. Another important advantage of the relatively blunt
bevel of the tip of the needle is that the vasculonervous sheath
that must be pierced by the needle in a plexus block can be pierced
only with a perceptible resistance. When the vasculonervous sheath
is penetrated, this resistance produces a perceptible "pop" which
is a reliable indication that the cannula tip has penetrated into
the nerve sheath and has reached the site intended for the
injection.
For the prevention of damage to the nerves or vessels, all that is
necessary is that the bevel at the outermost end of the needle tip
be made at a relatively blunt angle to the needle axis or adjacent
circumferential surface of the needle. The rest of the bevel,
however, could be made at a lower or sharper angle. Making the
entire bevel surface at a blunt angle increases the resistance
produced in the piercing of the vasculonervous sheath and thus
improves the reliability of the identification of the plexus that
is to be blocked.
For the use of the injection needle of the invention as an
"immobile needle", a flexible plastic tube approximately 25 to 35
cm long is connected by means of a Luer-Lok fitting to the base
part of the injection needle in a leak-proof manner. At the
opposite end of the tube, the injection syringe is also fastened by
a Luer-Lok fitting. The flexible extension makes it possible for
the injection needle to be held in position unaffected by the
palpation.
By means of the invention, therefore, the possibilities for the use
of immobile needles are substantially expanded and the plexus block
is simplified to such an extent that it can be performed even by
less experienced physicians without dangerous side effects for the
patients.
These and other objects and advantages of the invention will become
more apparent if they are considered in conjunction with the
following detailed description of the preferred embodiment of the
invention.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a diagrammatic representation of an embodiment of the
injection device of the invention, without an injection syringe,
and
FIG. 2 is a greatly enlarged view of the portion of the injection
needle forming the tip, as seen in the plane of the ground
bevel.
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the injection device of the invention is shown
diagrammatically in FIG. 1. It has a needle 1 of metal, referred to
hereinafter as the "cannula", which is provided at one end with a
base part 2 of plastic. The base 2 can be cemented, for example, to
the metal cannula. An injection syringe, not represented in the
drawing, can be connected to the base 2 either directly by a
Luer-Lok fitting or through an extension designated generally by
the reference number 3.
The cannula 1 has on its free end a relatively short needle tip 10
defined by a circumferential surface 11 and a ground bevel 12
intersecting the latter (FIG. 2). The intersection between the
bevel surface 12 and the circumferential surface 11 of the cannula
1 can be slightly rounded or dulled at the outermost end in order
further to reduce the danger of producing nerve lesions by the use
of the injection device. The bevel 12 is at a relatively blunt
angle .delta. to the cannula axis 13, so that the apex angle
.delta.'=.delta. is relatively blunt. In the case of an embodiment
that has proven practical, .delta. is approximately 45.degree.; the
angle .delta. should preferably range from about 40.degree. to
about 60.degree.. The size of the cannula 1 that has been tested in
practice is 25.times.0.55 mm, 24 gauge, so that at a bevel angle
.delta.=.delta.'=45.degree. a bevel 12 is formed which covers 0.55
mm of the length of the cannula. Also 26 gauge has been shown to be
useful, or 25 gauge. Further experiments have shown that the
maximum outer cannula diameter e should be about 0.55 mm, and the
length of the cannula should be in the range of from 25 to 50 mm.
The preferred needle length is 35 mm. This is in contrast to
epidural needles which have a size from 16 to 19 gauge.
The relatively blunt bevel angle .delta., which is more than twice
as great as the angle of the bevels of conventional injection
needles (.delta.<20.degree.), is important chiefly at the
outermost end of the needle tip 10, i.e., in the left half, as seen
in FIG. 2, of the needle between the circumferential surface 11 and
the cannula axis 13. The remainder of the bevel 12, however, could
be at a lower or more acute angle. The relatively steep slope of
the entire bevel 12 with respect to the cannula axis 13 as
represented in FIG. 2 is preferred, however, since this increases
the resistance encountered upon piercing through the vasculonervous
sheath and thus improves the reliability of the location of the
plexus that is to be blocked.
The base part 2 is cemented to the end of the cannula opposite the
tip 10, at the point marked 21. The cannula bore 14 (FIG. 2)
terminates in a tapered socket 22 in the base part 2. The tapered
socket 22 terminates in a mounting flange 23 which, in a Luer-Lok
fitting, participates in the positive attachment either of the
injection syringe or of the flexible extension tube 3.
By means of the flexible tube connection 3 represented in FIG. 1,
the cannula 1 can be used as an immobile needle and thus is
especially suitable for the blocking of peripheral nerves.
The extension 3 consists of a flexible plastic tube 30 of a length
of about 20 to 35 cm, whose ends are attached to complementary
fittings 31 and 32 of a Luer-Lok coupling. The fitting 31 is
coupled to the base part 2 by fitting a tubular tapered chuck 33
into the tapered socket 22, thereby producing a leak-proof junction
between the parts. The axial thrust required for the purpose is
produced by a screw cap 34 which is part of the fitting 31 and
whose helical internal thread 35 engages the flange 23 of the
needle base 2.
The fitting 32 on the opposite end of the tube 30 is of a
configuration similar to that of the base 2 of the cannula, so that
the chuck of the injection syringe can be coupled to the fitting 32
the same as it can to the base part 2. When the injection needle 1
is joined by the extension 3 to an injection syringe not shown in
the drawing, the needle can be held still in its proper place
during palpation and is not directly affected by the movements of
the syringe. It is important for the length of the tube 30 with the
fittings 31 and 32 to be just sufficient--namely not longer than 35
cm--such that it does not interfere with the use of the injection
device, but on the other hand the position of the cannula 1 will
not be disturbed by unavoidable movements of the syringe.
In the foregoing description the invention has been explained in
conjunction with an especially preferred embodiment. It is to be
noted, however, that the special details set forth are only for
purposes of illustration and the invention can be embodied in other
ways without departing from the idea of the invention and from the
scope of the appended claims.
* * * * *